1. Field of the Invention
The present invention relates to an inner-rotor-type motor and, more particularly, to an inner-rotor-type motor with cover plates.
2. Description of the Related Art
FIG. 1 shows a conventional inner-rotor-type motor 9 including a housing 91, a stator 92, a rotor 93 and a permanent magnet 94. The housing 91 has a compartment 910 receiving the stator 92. There is an assembling hole 921 arranged at the axial center of the stator 92, with the assembling hole 921 passing through the stator 92 from the top to the bottom thereof. The rotor 93 has a shaft 931 with an outer periphery where the permanent magnet 94 is fixed. The shaft 931 rotatably extends through the assembling hole 921. Two bearings 95 are mounted around the shaft 931, with the permanent magnet 94 being between the two bearings 95 and facing the stator 92.
In use, the stator 92 is controlled to proceed with energizing to react with the permanent magnet 94, and, then, the rotor 93 rotates. Furthermore, in order to prevent the permanent magnet 94 from hitting the stator 92 during rotation of the rotor 93 to avoid damage, there is a spacing between the permanent magnet 94 and the stator 92.
Generally, a motor is constructed by many components, which have complicated shapes and may be integrally formed by powder metallurgy, such as a core of the stator 92 and the permanent magnet 94. However, the rotor 93 is turning, and the motor 9 is vibrating during operation. This kind of situation will easily lead to generation of undesired powder parted from the components. The bearings 95 of the conventional inner-rotor-type motor 9 are often selected from ball bearings 951, and there are gaps formed between the shaft 931 and the bearings 95 and between an inner ring and an outer ring constructing the ball bearing 951. Because of gravity and vibration of the operating motor 9, the undesired powder may fall into the gaps to affect rotation of the shaft 931 in the bearings 95 and function of the ball bearing 951. Thus, non-smooth rotation of the rotor 93 as well as reduction of life of the motor 9 will result. Hence, there is a need for an improvement over the conventional inner-rotor-type motor 9.